MESSENGER-RNA EXPRESSION OF KIF1A, KIF1B, KIF2, KIF3A, KIF3B, KIF4, KIF5, AND CYTOPLASMIC DYNEIN DURING AXONAL REGENERATION

Mouse brain expresses multiple kinesin superfamily proteins (KIFs), wh ich are involved in vesicle transport. The expression of KIFs is devel opmentally regulated, and both the mRNA and proteins of KIF2 and KIF4 are expressed abundantly in the juvenile brain. To elucidate the role of individual kinesin superfamily motor proteins during regenerative o utgrowth of axons, we examined the mRNA expression of KIF1A, KIF1B, KI F2, KIF3A, KIF3B, KIF4, and KIF5 in adult mouse dorsal root ganglion c ells after sciatic nerve crush. Seven to fourteen days after the nerve crush, the mRNA expression pattern of neurofilament and beta-tubulin isotypes suggested that the regenerative outgrowth of axons was active . At these stages, levels of mRNA for KIF1A, KIF1B, KIF2, KIF3A, KIF3B , KIF4, and KIF5 were 50-80% of control. The levels of mRNA for KIF4, which are detected in juvenile brain but not in the adult, were under the detection limit in both control and regenerating dorsal root gangl ion cells. Because mRNA of neither KIF2 nor KIF4 increased significant ly, the results suggest that the gene expression of KIFs during regene ration does not recapitulate the embryonic development and support the hypothesis that different series of events take place during the rege nerative and embryonic outgrowths of axons. In contrast, mRNA for cyto plasmic dynein was slightly increased, up to 140%. This is consistent with the hypothesis that retrograde transport plays critical roles in regeneration such as the transport of neurotrophic factors.